Carbide-derived carbon importance

It is important to note that the commonly used term average pore size is insufficient to describe a complex pore structure, and it is even misleading for many porous materials because it does not reflect (i) the magnitude, and (ii) the modality of the pore size dispersion that is, how narrow the pore size distribution centers around one or several maxima. Only carbons with a very narrow pore size distribution, such as CNTs, some carbide-derived carbons (CDCs), and many template-produced carbons, exhibit a meaningful pore size average, whereas most activated carbons or hierarchic porous materials exhibit a much broader distribution of pore sizes. 

However, the electrodes which are used in supercapacitors have far more complex topologies than planar surfaces. The nanoporous carbons, such as the nanotubes, " cluster-assembled nanostructured carbons, nano-onions or carbide-derived nanoporous carbons have surfaces which are mostly curved, and can also contain many topological defects. It is important to understand how this impacts the structure of the adsorbed electrolytes and the resulting capacitance of the interface, even in the absence of confinement effects. 

Calcium Carbide and its Derivatives. Although hydrocarbon-based acetylene production has become mote important, eady manufacture of acetylene was based on manufacture of the iatermediate, calcium carbide [73-20-7J, CaC2. This ionic acetyUde is produced by reaction of lime and carbon ia electric-arc furnaces (16). 

Potassium cyanide, KCN.—The cyanide is manufactured by methods similar to those employed for the corresponding sodium derivative. Potassium ferrocyanide is heated either in absence of air, or with potassium carbonate and charcoal, or with sodium, the potassium cyanide being extracted by lixiviation with water or dilute alcohol. It is also obtained by the action of a mixture of steam and nitrogen on potassium carbonate or carbide,7 the manufacture of cyanides by the aid of atmospheric nitrogen being now an important industrial process. 

Carbon forms play important roles as intermediates, catalyst additives and deactivating species in Fischer-Tropsch synthesis on iron catalysts. Deactivation may be due to poisoning or fouling of the surface by atomic carbidic carbon, graphitic carbon, inactive carbides or vermicular forms of carbon, all of which derive from carbidic carbon atoms formed during CO dissociation (ref. 5). While this part of the study did not focus on the carbon species responsible for deactivation, some important observations can be made to this end. 

No carbonyl chemistry of scandium and yttrium has been reported yet and there is also no cyanide chemistry of these two elements although thiocyanato complexes of scandium [Sc(NCS)6]3 (bonded through nitrogen) are known. The important developments involving scandium or yttrium with carbon have involved the fullerene derivatives of these elements. There have been some scandium carbide systems prepared but these will be highlighted in the chemistry of the halides. 

Although the title of this book, Perspectives in Molecular Sieve Science, avoids the zeolite definition controversy, a large majority of the research reported here centers on traditional zeolites. Only three of the 39 chapters comprising the book deal with materials that are clearly nonzeolitic Two cover clay-type derivatives, and one deals with carbon molecular sieves. Not surprisingly, interest in these materials lies in their possible use as catalysts. Only four chapters present work on mineral zeolites and three on aluminum phosphate-type molecular sieves. Two of those chapters are by workers from Union Carbide, the laboratory that did the pioneering work in this field. It is surprising that other workers have not submitted papers on the aluminum phosphates, but perhaps this situation indicates that although much activity may be underway, laboratories hesitate to publish until patent positions are established in this potentially lucrative area. Union Carbide s synthetic faujasites (zeolites X and Y) and zeolite A receive the most attention, while ZSM-5-class materials are accorded more attention than zeolite A alone. This reflects the important roles that zeolites X and Y and ZSM-5 materials have already played as catalysts. 

Glass fibers, which are derived from a melt, were discussed in Chapters 4 and 5. Glass fibers, which are derived from a viscous solution, will be described in this chapter. The most important applications of glass fibers made by any process will be discussed in Chapter 6. Carbon fibers and ceramic carbide and oxide fibers, which are derived from solid precursor fibers, will be discussed, along with their applications, in Chapters 8 to 12,... 

Although silicon carbide, carborundum, was first synthesized before the turn of the century, new syntheses and applications for this important compound are still being developed. The name carborundum derives from its hardness (9.3 on the Mohs hardness scale) and was coined to indicate that SiC falls between carbon (diamond = 10.0) and corundum (sapphire, AI2O3 = 9.0). 

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